What Role Antagonists Play in the Study of Drugs?

Question

I am pretty unfamiliar to pharmacology. I'm doing a research on drug abuse, particularly opioids' mechanism of action. I encountered several times evidences that come from studies using **antagonists** especially **naloxone** that are to prove something is **'a specific opioid effect'**:> Opioid-induced miosis in the human ... This action is a specific> opioid effect as demonstrated by its antagonism by naloxone. I wanted to know the rationale behind these kind of conclusions. Also an elaboration on the role antagonists play in drug research will be appreciated.

Answer 1

The opioid antagonist naloxone has a high affinity for certain opioid receptors. The area gets complicated because of the various sub-types of receptors, but for this answer we'll just refer to them as opioid receptors. The drug naloxone is used in the research laboratory because it is know to block the opioid receptor, so if any other drug acts at this receptor, naloxone can be use to block it or compete with it. If this other drug does NOT act at the opioid receptor, then naloxone should have no effect on its action. This is a commonly used approach in pharmacology. By definition, an antagonist will block the effects of the natural ligand and/or other agents that act at that particular receptor.